Parallel plate capacitor system for determining impedance characteristics of material under test (MUT)

ABSTRACT

Various aspects of the disclosure relate to evaluating the electromagnetic impedance characteristics of a material under test (MUT) over a range of frequencies. In particular aspects, a system includes: an electrically non-conducting container sized to hold the MUT, the electrically non-conducting container having a first opening at a first end thereof and a second opening at a second, opposite end thereof; a transmitting electrode assembly at the first end of the electrically non-conducting container, the transmitting electrode assembly having a transmitting electrode with a transmitting surface; and a receiving electrode assembly at the second end of the electrically non-conducting container, the receiving electrode assembly having a receiving electrode with a receiving surface, wherein the receiving electrode is approximately parallel with the transmitting electrode, and wherein the transmitting surface of the transmitting electrode is larger than the receiving surface of the receiving electrode.

PRIORITY CLAIM

This application claims priority to U.S. Provisional Patent ApplicationNo. 62/661,682, filed on Apr. 24, 2018, which is herein incorporated byreference in its entirety.

TECHNICAL FIELD

This disclosure relates generally to material testing. In particular,this disclosure relates to determining impedance characteristics ofmaterials over a range of frequencies.

BACKGROUND

In U.S. Pat. No. 7,219,024, a system is described for conductingelectromagnetic impedance spectroscopy to non-invasively determine thein-place compaction (i.e., density) and moisture of various engineeringmaterials, with specific interest in soils. The system uses an algorithmto relate the measured impedance of the soil over a frequency range tothe compaction level (density) of the soil and the moisture level. Inthis conventional system, a user inputs the soil characteristics asdetermined by standard laboratory tests, which provide the plasticitylimits (ASTM D4818, a standard issued by ASTM International, WestConshohocken, Pa.), particle size distribution (ASTM D422), and Proctorlimits (ASTM D698 and D1557) of the soil. The algorithm then correlatesthe measured impedance over a range of frequencies to the compacted soildensity and moisture level in the field. In order to make thesecorrelations, the conventional system must develop a library of theimpedance characteristics of soils with varying levels of compaction andmoisture levels. Real-time calculations and correlations made by thesystem algorithm are predicated on this library.

In conventional approaches, the library is developed with a combinationof testing procedures in the laboratory and in the field. The laboratorytesting has limitations due to the size of the test fixture capableaccommodating the compaction method, as well as the amount of soilrequired to perform an in-laboratory test. Additionally, it is difficultto reliably recreate field compaction results in a laboratory due to themethods of field compaction, control of the compaction variation withdepth, the distribution of moisture, and other factors. While fieldtesting is more accurate than laboratory testing in replicating fieldcompaction methodologies, it is limited in terms of the type of soilsthat can be tested. Additionally, changes in weather conditions willinevitably limit the conditions of a field test. As examples, weatherwill affect variables such as the amount of precipitation in a sample,timing of the precipitation, ambient temperature, and amount andduration of direct sun exposure.

SUMMARY OF THE INVENTION

All examples and features mentioned below can be combined in anytechnically possible way.

Various aspects of the disclosure overcome challenges in conventionalapproaches for developing a soil compaction library. In particularaspects, a material testing system and related method are disclosed,where the system is configured to conduct reliable material compactiontesting across a range of frequencies. The system is configured tomeasure the impedance of a material over a range of frequencies withcontrolled amounts of moisture and compaction levels. In particularaspects, the system is configured to measure the impedance of smallsamples of material (e.g., soil) in a laboratory or other setting.

An aspect of the disclosure includes the preparation of the materialunder test (MUT) by compaction of the MUT (e.g. soils) within acylindrical container as specified in ASTM Standard D4253.

Additional aspects of the disclosure allow for the placement of varioustypes of materials that may be tested for their impedancecharacterization over a range of frequencies without first beingsubjected to the compaction process.

Additional aspects of the disclosure enable impedance characterizationof materials over a range of frequencies. In some particular aspects,electromagnetic impedance characterization of a (MUT) is performed overa range of frequencies, e.g., using a parallel plate electrode geometrywithin a non-conducting container where an electrode in communicationwith the MUT transmits an electromagnetic signal over a range offrequencies through the MUT to a receiving electrode. The electrodes canbe connected to a signal generator/analyzer which communicate theresults to a computing device. The transmitting electrode has aconductive backer ground plate which acts as the back plane of theelectrode and encloses a volume with the electrode. The receivingelectrode has a conductive backer ground plate that extends from thefront plane of the electrode and at least partially surrounds theelectrode to enclose a volume with the electrode. The transmittingelectrode size can be larger than the receiving electrode in order tocontrol the electric field lines passing through the MUT from thetransmitting electrode to the receiving electrode.

Various particular aspects of the disclosure relate to evaluating theelectromagnetic impedance characteristics of a material under test (MUT)over a range of frequencies. In some particular aspects, a systemincludes: an electrically non-conducting container sized to hold theMUT, the electrically non-conducting container having a first opening ata first end thereof and a second opening at a second, opposite endthereof; a transmitting electrode assembly at the first end of theelectrically non-conducting container, the transmitting electrodeassembly having a transmitting electrode with a transmitting surface;and a receiving electrode assembly at the second end of the electricallynon-conducting container, the receiving electrode assembly having areceiving electrode with a receiving surface, wherein the receivingelectrode is approximately parallel with the transmitting electrode, andwherein the transmitting surface of the transmitting electrode is largerthan the receiving surface of the receiving electrode.

Additional particular aspects of the disclosure relate to evaluating theelectromagnetic impedance characteristics of a material under test (MUT)over a range of frequencies. In some particular aspects, a systemincludes: a container that is lined with a non-conducting liner. Thecontainer and non-conducting liner are sized to hold the MUT, thecontainer having a first opening at a first end thereof and a secondopening at a second, opposite end thereof; a transmitting electrodeassembly at the first end of the container, the transmitting electrodeassembly having a transmitting electrode with a transmitting surface;and a receiving electrode assembly at the second end of the container,the receiving electrode assembly having a receiving electrode with areceiving surface, wherein the receiving electrode is approximatelyparallel with the transmitting electrode, and wherein the transmittingsurface of the transmitting electrode is larger than the receivingsurface of the receiving electrode.

Additional particular aspects relate to a method for determining anelectromagnetic impedance characteristic of a material under test (MUT).In some cases where the MUT is subjected to the compaction process, themethod includes: with the compacted MUT (e.g. soil) in a testing systemincluding: a container having a first opening at a first end thereof anda second opening at a second, opposite end thereof; and a transmittingelectrode assembly at the first end of the container, the transmittingelectrode assembly having a transmitting electrode with a transmittingsurface, including having the MUT on the transmitting electrode assemblyin the container; sealing a bottom of the container; placing a receivingelectrode assembly at the second end of the container over the MUT, thereceiving electrode assembly having a receiving electrode with areceiving surface, wherein the receiving electrode is approximatelyparallel with the transmitting electrode, and wherein the transmittingsurface of the transmitting electrode is larger than the receivingsurface of the receiving electrode; transmitting a set ofelectromagnetic signals from the transmitting electrode, through the MUTto the receiving electrode; and determining a characteristic of the MUTbased upon a change in the set of electromagnetic signals over a rangeof frequencies from the transmitting electrode to the receivingelectrode.

Additional particular aspects relate to a method for determining anelectromagnetic impedance characteristic of a material under test (MUT).In some cases where the MUT is not subjected to the compaction process,the method includes: placing the MUT in a testing system including: acontainer sized to hold the MUT, the container having a first opening ata first end thereof and a second opening at a second, opposite endthereof; and a transmitting electrode assembly at the first end of thecontainer, the transmitting electrode assembly having a transmittingelectrode with a transmitting surface, the MUT being placed on thetransmitting electrode assembly in the container; sealing a bottom ofthe container; placing a receiving electrode assembly at the second endof the container over the MUT, the receiving electrode assembly having areceiving electrode with a receiving surface, wherein the receivingelectrode is approximately parallel with the transmitting electrode, andwherein the transmitting surface of the transmitting electrode is largerthan the receiving surface of the receiving electrode; transmitting aset of electromagnetic signals from the transmitting electrode, throughthe MUT to the receiving electrode; and determining a characteristic ofthe MUT based upon a change in the set of electromagnetic signals over arange of frequencies from the transmitting electrode to the receivingelectrode.

Implementations may include one of the following features, or anycombination thereof.

In certain cases, the transmitting electrode assembly further includes:a transmitting electrode backer ground plate at least partiallysurrounding the transmitting electrode, the transmitting electrodebacker ground plate being electrically grounded and insulated from thetransmitting electrode, wherein the transmitting electrode backer groundplate extends from a plane formed by the transmitting electrode andcreates an electrically isolated volume proximate to the transmittingelectrode. In particular aspects, the transmitting electrode backerground plate is formed of an electrically conductive material andincludes a recess corresponding with the transmitting electrode, andwherein the plane formed by the transmitting electrode is substantiallyparallel with a surface of the MUT.

In some embodiments, the receiving electrode assembly further includes:a receiving electrode backer ground plate at least partially surroundingthe receiving electrode, the receiving electrode backer ground platebeing electrically grounded and insulated from the receiving electrode,wherein the receiving electrode backer ground plate extends from a planeformed by the receiving electrode and creates an electrically isolatedvolume proximate to the receiving electrode. In certain cases, thereceiving electrode backer ground plate is formed of an electricallyconductive material and includes a recess corresponding with thereceiving electrode, and wherein the plane formed by the receivingelectrode is substantially parallel with a surface of the MUT.

In particular embodiments, during operation of the system, thetransmitting electrode and the receiving electrode are in directphysical contact with the MUT and electrically non-conductive with theMUT.

In certain cases, the system further includes a signalgenerator/analyzer coupled with the transmitting electrode and thereceiving electrode, the signal generator/analyzer comprising agenerator component configured to initiate transmission of a set ofelectromagnetic signals over a range of frequencies from thetransmitting electrode, through the MUT, to the receiving electrode, andan analyzer component configured to detect a change in the set ofelectromagnetic signals from the transmitting electrode to the receivingelectrode. In some aspects, the system further includes a computingdevice coupled with the signal generator/analyzer, wherein the computingdevice is configured to determine a characteristic of the MUT based uponthe change in the set of electromagnetic signals from the transmittingelectrode to the receiving electrode, wherein determining thecharacteristic of the MUT comprises: determining a difference in anaspect of the set of electromagnetic signals over a range offrequencies; comparing the difference in the aspect to a predeterminedthreshold; and determining the characteristic of the MUT based upon thecompared difference.

In particular embodiments, the transmitting electrode and the receivingare aligned in parallel with one another.

In certain cases, the container and/or the electrically non-conductingliner includes plastics such as polyester, polyethylene, polyvinylchloride (PVC), polytetrafluoroethylene (Teflon), poly carbonate, and/orvarious fiber glass reinforce epoxy laminate materials (e.g. FR-4). Insome cases, the container and/or the electrically non-conducting lineris formed of a poly methyl methacrylate (PMMA or acrylic), which issubstantially transparent and allows for visual observation of thetesting process.

In some aspects, the container or the liner has a cylindricalcross-section, rectangular cross-section, or oblong cross-section, takenin a direction perpendicular to a primary axis thereof.

In particular implementations, the container includes at least twodistinct sections. In certain cases, the transmitting electrode has adiameter larger than an inner diameter of the container, and one of theat least two distinct sections comprises a seat for supporting anoverhang portion of the transmitting electrode.

In particular implementations that include a container with anelectrically non-conducting liner, the electrically non-conducting linerincludes at least two distinct sections. In certain cases, thetransmitting electrode has a diameter larger than an inner diameter ofthe container and one of the at least two distinct sections of theelectrically non-conducting liner includes a seat for supporting anoverhang portion of the transmitting electrode.

In certain embodiments, the transmitting electrode assembly and thereceiving electrode assembly are shaped to coincide with across-sectional shape of the first opening and second opening,respectively, of the container.

In some aspects, the transmitting electrode assembly and the receivingelectrode assembly are substantially contained within the container.

In particular cases, the transmitting electrode assembly and thereceiving electrode assembly are sized to complement an opening in asoil compaction device.

In some aspects, a testing method can further include the measurement ofsolid materials that are not of a size or shape to fit within thecontainer.

In certain embodiments, a solid material under test may be placeddirectly on the transmitting electrode assembly with the receivingelectrode assembly being placed on top of the MUT and aligned with thetransmitting electrode without an enclosing container.

In some particular aspects, a system for measuring an electromagneticimpedance characteristic of a material under test (MUT) includes: atleast one electrically non-conducting support sized to physicallysupport the MUT; a transmitting electrode assembly positioned on a firstside of the MUT, the transmitting electrode assembly having: atransmitting electrode with a transmitting surface; and a transmittingelectrode backer ground plate at least partially surrounding thetransmitting electrode, the transmitting electrode backer ground platebeing electrically grounded and insulated from the transmittingelectrode, wherein the transmitting electrode backer ground plateextends from a plane formed by the transmitting electrode and creates anelectrically isolated volume proximate to the transmitting electrode;and a receiving electrode assembly positioned on a second side of theMUT opposite the first side of the MUT, the receiving electrode assemblyhaving a receiving electrode with a receiving surface, wherein thereceiving electrode is approximately parallel with the transmittingelectrode, and wherein the transmitting surface of the transmittingelectrode is larger than the receiving surface of the receivingelectrode.

In particular cases, the receiving electrode has a backer ground plateat least partially surrounding the transmitting electrode, the receivingelectrode backer ground plate being electrically grounded and insulatedfrom the receiving electrode, wherein the receiving electrode backerground plate extends from a plane formed by the transmitting electrodeand creates an electrically isolated volume proximate to thetransmitting electrode.

In certain implementations, the MUT is a solid material, and an outerdimension of the MUT extends beyond an outer dimension of the at leastone electrically non-conducting support such that the at least oneelectrically non-conducting support does not envelop the MUT.

In particular cases, the solid material includes a solid concrete sampleor a solid asphalt sample.

In some implementations, the MUT includes soil.

In certain implementations, the MUT includes a granular material suchgrains.

In certain implementations, the MUT includes a liquid such as milk,oils, or other organic and inorganic fluids.

In some cases, the transmitting surface is configured to be placed indirect physical contact with the MUT, where the transmitting electrodebacker ground plate is electrically conducting, and where the plane isformed by the rear surface of the transmitting electrode.

Two or more features described in this disclosure, including thosedescribed in this summary section, may be combined to formimplementations not specifically described herein.

The details of one or more implementations are set forth in theaccompanying drawings and the description below. Other features, objectsand advantages will be apparent from the description and drawings, andfrom the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The embodiments of this disclosure will be described in detail, withreference to the following figures, wherein like designations denotelike elements, and wherein:

FIG. 1 shows a cross-sectional view of a system according to variousembodiments of the disclosure.

FIG. 2 shows a compaction fixture from FIG. 1 attached to a vibrationdevice according to various additional embodiments of the disclosure.

FIG. 3 shows a system according to various further embodiments of thedisclosure.

FIG. 4 shows an additional system according to various embodiments ofthe disclosure.

FIG. 5 shows another system according to various embodiments of thedisclosure.

FIG. 6 shows a system according to various additional embodiments of thedisclosure.

FIG. 7 shows a close-up cross-sectional view of the system of FIG. 5.

FIG. 8 is a data flow diagram illustrating connections in a systemincluding a signal generator/analyzer, according to various embodimentsof the disclosure.

FIG. 9 is an additional data flow diagram illustrating connections in asystem including a signal generator/analyzer, according to variousembodiments of the disclosure.

FIG. 10 shows electric field lines during a testing operation with thesystem of FIG. 5.

FIG. 11 shows electric field lines during a testing operation with thesystem of FIG. 6.

FIG. 12 shows a cross-sectional view of computed field lines associatedwith the system of FIG. 6.

FIG. 13 shows a cross-sectional view of a system according to anadditional embodiment for testing a solid material under test without anenclosing electrically non-conducting container.

FIG. 14 is an additional data flow diagram illustrating connections inthe system of FIG. 13, including connections with a signalgenerator/analyzer, according to various embodiments of the disclosure.

It is noted that the drawings of the various implementations are notnecessarily to scale. The drawings are intended to depict only typicalaspects of the disclosure, and therefore should not be considered aslimiting the scope of the implementations. In the drawings, likenumbering represents like elements between the drawings.

DETAILED DESCRIPTION

As noted herein, this disclosure relates generally to material testing.In particular, this disclosure relates to determining impedancecharacteristics of materials. In some aspects, impedance characteristicsof materials are determined over a range of frequencies.

One approach disclosed according to embodiments includes modifying the(soil) compaction method described in ASTM Standard D4253 (standardissued by ASTM International, West Conshohocken, Pa.), to comply withthe disclosed system including a parallel plate capacitor and anelectrically non-conducting container. This approach can include placinga variety of materials with specific levels of moisture in the disclosedcompaction device and compacting each of those material samples todifferent levels of compaction. After compaction, the compaction deviceis removed and a component of the disclosed parallel plate capacitor isplaced on the surface of the soil sample. After placement of theparallel plate capacitor, electromagnetic signals are generated over arange of frequencies and transmitted through the material, and theimpedance characteristics of the material sample are measured andstored.

The electromagnetic signals may be generated by any number of methodsknown in the art. For example, standard commercial instruments such as aKeysight network analyzer or impedance analyzer may be used. Also, thecircuits described in U.S. Pat. No. 7,219,024 or U.S. Patent ApplicationNo. 62/434,789 (both of which are incorporated by reference in theirentirety) may be used. While one method of material compaction isdescribed by ASTM Standard D4253 (standards documentation herebyincorporated by reference in its entirety), other methods of material(e.g., soil) compaction are described in literature but are not codifiedin an ASTM Standard. One of these approaches involves use of a GyratoryCompactor, which is a conventional piece of laboratory equipment usedfor asphalt testing, and manufactured by companies such as TroxlerElectronic Laboratories, Gilson Company, Humboldt Manufacturing, andPine Test Equipment. Another device is the California KneadingCompactor, which is described in California Test 104 for soils and ismanufactured by Forney LP. The Gyratory Compactor and CaliforniaKneading Compactor are automatic compacting systems. Additional testscan be performed, e.g., with a manual system, such as the MarshallCompactor. However, this manual system approach has various drawbackswhen compared with the automatic compacting systems.

While the systems and testing approaches described herein are applicableto many materials, portions of the discussion will focus on applicationsto the electromagnetic characterization (e.g., over a range offrequencies) of controlled samples of soil of varying composition,moisture levels, and degrees of compaction utilizing a standardcompaction method.

FIG. 1 illustrates a cross-section of a system 100 which is incompliance with ASTM Standard D4253. This system 100 includes anon-conducting cylindrical container 104 into which a material undertest (MUT) sample 101 is placed. In various implementations, the MUTsample 101 includes a soil sample. A compression weight 106 is placed ontop of the MUT sample (or simply, MUT) 101 to compress the soil. In someexamples, the weight of compression weight 106 is determined to providea compressive force of 2 lbs/in² (13.8 kPa) when combined withcharacteristics of the vibration device 107 (e.g., shaker table, FIG.2), as specified in ASTM Standard D4253. However, in otherimplementations, the MUT 101 can include materials that can flow intothe cylindrical volume. These can include, e.g., granular materials suchas soils and grains, slurries such as fresh concrete, and liquids.System 100 can also be used to test solids that are configured to fitwithin a cylindrical testing apparatus.

There are other infrastructure testing specifications that may be usedwith the subject apparatus(es) disclosed herein. Specifically, a soilProctor test (ASTM D698 and D1557) may be tested. For asphalt, the corescut from finished roads (ASTM D1188, D3203, D3549, and D5361) may betested as well as the asphalt gyratory samples (ASTM D3387, D6925, andD7229). Additionally, concrete cylinders which are collected and agedper ASTM C31, C39, C172, and C192 may be characterized with the subjectapparatus.

While some of the description for this disclosure focuses on its usewith soils, in other implementations, the MUT can include materials thatcan flow into the cylindrical volume, e.g., granular materials such assoils and grains, slurries such as fresh concrete, and liquids. Forexample, U.S. Pat. No. 10,161,893 (“Characterization of material undertest (MUT) with electromagnetic impedance spectroscopy”, filed as U.S.patent application Ser. No. 14/825,542, and herein incorporated byreference in its entirety) describes a system for the field use ofelectromagnetic impedance to characterize wet concrete as it isdelivered to a construction site. The systems of the current disclosuremay be used to secure the dielectric and impedance characterization ofwet concrete to be used in the development of the algorithms for usewith the system of U.S. Pat. No. 10,161,893. The systems disclosedherein may also be used in characterizing dielectric and impedancecharacteristics various organic liquids such as dairy products (milk),olive oil, fruits, other vegetable oils, cookies, pork and fish. Thesensor system of the current disclosure may be used to secure thedielectric and impedance characterization of various liquids to be usedin the development of the algorithms for the correlation with physicalproperties of interest for those liquids.

Referring to FIG. 1, flanges 105 are illustrative of one mountingmechanism for assembling the system 100, e.g., to maintain the positionof compression weight 106 on MUT sample 101. In contrast to theconventional systems which use a fixed base supporting the compressedsoil sample, system 100 includes a parallel plate electrode assemblywhich acts as the base of the test cylinder. This parallel plate(transmitting) electrode assembly 201 includes an electrode 102 and a(conductive) backer ground plate 103. The electrode 102 is supported bythe backer ground plate 103, which is in turn supported by anon-conducting support member 119 (formed of any non-conducting materialdescribed herein). Additional aspects of a backer ground plate can befound in U.S. Provisional Patent Application No. 62/619,275, which ishereby incorporated by reference in its entirety.

FIG. 2 shows an assembly 200 including the system 100 mounted to avibration device (also referred to as a shaker table) 107. Vibrationdevices such as shaker tables are well known in the art and variousacceptable types are specified in ASTM Standard D4253.

The MUT sample 101 (FIG. 1) is selected to be either representative of ageneral class of materials (e.g., soils) as specified in ASTM StandardD2487, or a material sample from a specific location (e.g., soil from aconstruction site or other area of interest). In various embodiments, inthe case of soil, the sample 101 is oven dried per ASTM Standard D4442.Various amounts of de-ionized water are added to the dry soil to providefor a test matrix of gravimetric water content which is defined asfollows:

$\theta_{g} = {\frac{m_{water}}{m_{dry}} = \frac{m_{wet} - m_{dry}}{m_{dry}}}$where θ_(g) is the gravimetric water content, m_(water) is the weight ofwater added, m_(dry) is the weight of the dry soil sample, and m_(wet)is the combined weight of the water and dry soil in the sample. In orderto adjust for the salinity of soil found naturally, sodium chloride(NaCl) can be added to the de-ionized water. In these cases, theimpedance characteristic will be a function of the soil type, watercontent, salinity, and the degree of compaction.

The total volume of a soil sample, V_(total), is made up of threecomponents: the volume of the dry soil, V_(dry); the volume of water,V_(wet); and the volume of air, V_(air). When soil is compacted, thevolume of air is reduced, but the volumes of water and dried soil remainconstant so that the total volume, V_(total), is reduced. There is anoptimum level of water content which produces the maximum value of drydensity. This is referred to as the Proctor maximum and is determined byASTM Standard Tests D698 and D1557.

The soil characteristics that are desired to be correlated to theimpedance characteristics over a range of frequencies are thegravimetric moisture content and the dry density. The dry density isdefined as follows:

$\rho_{dry} = \frac{m_{dry}}{V_{total}}$where ρ_(dry) is the density of the dried soil, m_(dry) is the weight ofthe dry soil, and V_(total) is the total volume of sample. The type ofsoil as defined by the ASTM classifications selected for testing and themasses of water and dry soil in the sample are determined in the testprotocol specifications. The only variable that is changed is thecompaction of the soil, which is a function of the change of volumeachieved by the compaction and the reduction of the volume of air,V_(air). Since the area of the compaction cylinder is known, thedetermination of volume depends only on the measurement of the height ofthe soil sample at various compaction levels. Thus, the volume is givenby this relation:V _(total) =A _(cyl) *H _(sample)where A_(cyl) is the internal area of the cylinder and H_(sample) is theheight of the soil sample at various levels of compaction. The height ofthe compacted MUT sample 101 may be measured by various means which arewell known in the art. ASTM D4253 specifies use of a dial indicator tomeasure the compacted height. However, there are other known methodswhich provide a digital output and potentially better precision than thedial indicator.

An alternative approach for determining the height to the MUT sample 101is to use a spacer or a stop to fix the height of the compaction processor the MUT sample 101.

Once the MUT sample 101 is compacted to a desired test level, thecompressive weight 106 (FIG. 1) is removed and a second part of theparallel plate electrode assembly (receiving electrode assembly), asshown in system 300 in FIG. 3, is placed on the top of the compressedMUT sample 101. This receiving electrode assembly 210 includes anelectrode 108 and a (conductive) backer ground plate 109.

FIG. 4 presents a system 300A, depicting an alternate approach for theplacement of a transmitting electrode assembly, depicted as transmittingelectrode assembly 301. As shown, the transmitting electrode 302 extendsbeyond the inner diameter (ID) of the container. In this embodiment, thecontainer 104 includes at least two distinct sections 331 and 332. Asnoted herein, the transmitting electrode 302 has a diameter larger thanan inner diameter (ID) of the container 104. In some cases, one of thesections 331 of the container 104 includes a seat 315 for supporting anoverhang portion of the transmitting electrode 302. In system 300A inFIG. 4, the supporting section is shown as 331. The conductive backerground plate 303 extends from the rear face of the transmittingelectrode 302 and partially surrounds the transmitting electrode 302,enclosing a volume 325 proximate to the transmitting electrode 302. Thediameter of the conductive backer ground plate 303 is sized to fit theinternal diameter of the cylindrical container 104 (e.g., within the IDof both sections 331 and 332). In the system 300A, the supporting member119 (FIGS. 1, 3, 5, and 7) may not be required to support thetransmitting electrode 302 and adjoining backer ground plate 303. System300A can be operated in a similar manner as other systems describedherein.

FIG. 5 presents an additional configuration of a system 400, formaterial characterization, similar to system 300 in FIG. 3. In system400, as compared with the container 104 in FIG. 3, the container isformed of two components, a conducting structural member 404 and anelectrically non-conductive liner 440. Conductive portions of the system400 (as well as conductive portions of other systems noted herein) maybe formed of conventional conductive materials such as metals, e.g.,steel and aluminum. The non-conducting portions of the system 400 (aswell as non-conducting portions of other systems noted herein) can beformed of materials such as plastics (e.g., polyester, polyethylene,polyvinyl chloride (PVC), polytetrafluoroethylene (Teflon), polycarbonate, and/or various fiber glass reinforce epoxy laminate materials(e.g. FR-4), and in some cases, can be formed of a poly methylmethacrylate (PMMA or acrylic), which is substantially transparent andallows for visual observation of the testing process. The liner 440 canbe located radially inboard of the conducting structural member 404, andmay be adhered, fastened, integrally formed, or otherwise coupled withthe conducting structural member 404.

FIG. 6 presents an alternate configuration, shown as system 500, for thecylindrical container 104 in FIG. 4. In this case, system 500 shows acontainer 530 formed of four components 531-534. These include twoconducting structural members 531 and 532, and two electricallynon-conducting members 533 and 534. The conductive components may beformed of conductive materials described herein, while thenon-conducting liner may be formed of non-conducting materials describedherein. In some particular implementations, the container 530 iscylindrical. Similarly to the system 300 in FIG. 4, the transmittingelectrode 502 in system 500 extends beyond the inner diameter (ID) ofthe container 530. In various implementations, the lower liner 533includes a seat 535 for supporting an overhang portion of thetransmitting electrode 502. The conductive backer ground plate 503extends from the rear face of the transmitting electrode 502 andpartially surrounds the transmitting electrode 502, enclosing a volume540 proximate to the transmitting electrode 502. The diameter of theconductive backer ground plate 503 is sized to fit the internal diameterof the lower liner 533 (which has the same inner diameter as the upperliner 534). As compared with other implementations herein, thesupporting member 119 (FIGS. 1, 3, 5, and 7) may not be required tosupport the transmitting electrode 502 and adjoining backer ground plate503 in the system 500 of FIG. 6.

FIG. 7 shows an enlarged view of system 400 (FIG. 5), includingadditional detailed illustration of the electrode assemblies 401, 410and electrical connections with a signal generator and analyzer (notshown). An example signal generator and analyzer 113 is illustrated,with the electrical connections between the electrode assemblies and thesignal generator/analyzer shown in the data flow diagram in FIG. 8.Returning to FIG. 7, a lead 110 from a signal generator/analyzer isshown connected with the transmitting electrode 402. An additional lead111 is shown connecting the receiving electrode 408 with the signalanalyzer/generator. Lead 110 is used to initiate transmittal of a signalfrom the transmitting electrode 402, through the MUT 101, and lead 111is used to return the received signal (received at the receivingelectrode 408) to the signal generator/analyzer after passing throughthe MUT 101. Additional leads 112 are shown connecting each of theconductive backer ground plates 403, 409 to the system ground (FIG. 8).In various embodiments, the (transmitting) diameter of the transmittingelectrode 402 is larger than the (receiving) diameter of receivingelectrode 408. In some implementations, the diameter of the transmittingelectrode 402 is shown as approximately equal to the interior diameter(ID) of the container. In all implementations of system 400, the(transmitting) diameter of the transmitting electrode 402 is larger thanthe (receiving) diameter of the receiving electrode 408 for reasonsnoted herein.

Referring to system 400 in FIG. 7 and the corresponding data flow inFIG. 8, the backer ground plate 403 for the transmitting electrode 402and the backer ground plate 409 for the receiving electrode 408 areconnected to a system ground from the signal generator/analyzer 113. Invarious embodiments, it is beneficial that the electric potential of thebacker ground plates 403 and 409 be equal. The parasitic capacitance ofthe volume created between the respective backer ground plates andelectrodes (volumes 420 and 430) are affected by the potential of boththe backer ground plate and the corresponding transmitting and receivingelectrodes. By controlling the electric potential of the two backerground plates such that those potentials are identical, the designvalues for the parasitic capacitances can be more easily defined andmaintained. In certain implementations, the transmitting electrodebacker ground plate 403 can have a diameter approximately equal to theID of the (e.g., cylindrical) container 404 with the (e.g.,non-conducting) liner 440. The transmitting electrode backer groundplate 403 at least partially encloses a volume 420 behind the electrode402. The receiving electrode backer ground plate 409 has a surface thatis coplanar with the surface of receiving electrode 408 and at leastpartially encloses a volume 430 behind the receiving electrode 408. Bothbacker ground plates 403 and 409 are electrically insulated from theirrespective electrodes 402 and 408 by an air gap of distance d_(T) forthe transmitting electrode assembly 401 and of distance d_(R) for thereceiving electrode assembly 410.

The conductive backer ground plates 403, 409 around the transmittingelectrode 402 and the receiving electrode 408 can help to control theparasitic capacitances generated by the electric field lines whichtraverse between the electrodes 402, 408. These backer ground plates403, 409 can be used to control the electric field lines between theelectrodes 402, 408 as they pass through the MUT sample 101. As thetransmitted electromagnetic signal is scanned over a range offrequencies, the amplitude of the electric potential of the signalremains approximately constant and controls the potential of the groundplate. The enclosed volume 420 created by the backer ground plate 403 atleast partially surrounding the transmitting electrode 402 helps tomitigate the parasitic capacitance (e.g., by designing the enclosedvolume 420 and the distance d_(T) based upon a computation of the systemimpedance using a computational tool such as Comsol's Multiphysics)between the backer ground plate 403 and the transmitting electrode 402,and is controlled to limit the effects of the parasitic capacitance onthe impedance measurements. The volumes 420 and 430 are determined bythe distances d_(T) and d_(R) and the diameter of the electrodes 402 and408 (D_(TX) and D_(RX)). The optimization attempts to balance thecurrent drive requirements of the transmit circuit, the parasiticinductances of the wiring, signal strength, and immunity with respect tonoise and inductive/capacitive coupling. This results in a systemspecific solution. An example range of the ratios of d_(R)/D_(RX) andd_(T)/D_(TX) are from 1:1000 to 1:1.

The receiving electrode 408 and its corresponding backer ground plate409 act in a different manner. The signal arriving at the receivingelectrode 408 after passing through the MUT sample 101 varies with thematerial type (e.g., soil type, water content, compaction level, andfrequency). As the transmitted signal from electrode 402 passes throughthe MUT sample 101, the strength of the signal (magnitude) isattenuated, and the phase relation is changed. As such, the potential ofthe signal and its phase relative to the transmitted signal is quitevariable (by material type), and unknown a priori. The parasiticcapacitance due to the field between the receiving electrode 408 and itsbacker ground plate 409 has a larger effect on the measurement (whencompared with the transmitting electrode 402 and its backer ground plate403) due to the attenuation of the transmitted signal at the receivingelectrode 408. Therefore, the ability to reduce and control theparasitic capacitance for the receiving electrode 408 is significant tothe quality of the data measured. Again, this is achieved by thecombination of controlling the potential of the backer ground plate 409and by designing the volume 430 enclosed by the receiving electrode 408and the conductive backer ground plate 409 based upon a computation ofthe system impedance, e.g., by use of a computational tool such asComsol's Multiphysics.

FIG. 8 is a schematic data flow diagram illustrating connections betweenthe electrodes 402, 408, the signal generator/analyzer 113 and acomputing device 115 configured to determine characteristics of the MUTsample 101. The computing device 115 can include any conventionalcomputing architecture capable of performing processes as describedherein and can be programmed to perform particular functions. Thecomputing device 115 can include one or more processors and a memory,which may store program code and/or program logic for performing variousfunctions according to embodiments. As noted herein, the system ground112 of the signal generator/analyzer 113 is connected to thetransmitting conductive backer ground plate 403 and the receivingconductive backer ground plate 409.

The electrical connections illustrated in FIG. 8 can be applicable tosystems 200, 300, 300A, 400, and 500, although they are shown in thisexample as connections made with system 400.

As noted herein, the signal generator/analyzer 113 may includeconventional commercial instruments such as a Keysight network analyzeror impedance analyzer, or circuits such as those described in U.S. Pat.No. 7,219,024 or U.S. Patent Application No. 62/434,789 (each of whichis incorporated by reference in its entirety). The transmitting (orhigh) side 110 of the signal generator/analyzer 113 is connected to thetransmitting electrode (e.g., transmitting electrode 102 in FIG. 3, ortransmitting electrode 402 in FIG. 7). The receiving (or low) side 111of the generator/analyzer 113 is connected to the receiving electrode(e.g., receiving electrode 108 in FIG. 3, or receiving electrode 408 inFIG. 7). Both the transmitting backer ground plate (e.g., transmittingbacker ground plate 103 in FIG. 3, or transmitting backer ground plate403 in FIG. 7) and the receiving backer ground plate (e.g., receivingbacker ground plate 109 in FIG. 3, or receiving backer ground plate 409in FIG. 7) are connected to the ground 112 of the signalgenerator/analyzer 113. The signal generator/analyzer 113 is alsoconfigured to analyze the signal at each frequency in the range offrequencies used. The signal that is transmitted through the MUT sample101 is attenuated and the phase shifted during the transmission. Theanalyzer function of the signal generator/analyzer 113 records thechange in signal magnitude and phase between the transmitted andreceived signal for each test frequency. These data are transmitted assignal comparison data 114 to the computing device 115. The measuredimpedance of MUT sample 101 is computed for each frequency in the rangeof test frequencies (e.g., the range of frequencies for soil testing isfrom 100 kHz to 100 MHz) and correlated with the other test data (e.g.,soil characteristics, water mass, dry soil mass and compacted volume) todevelop the algorithm for the correlation of the measure impedancecharacteristics to soil dry density and gravimetric moisture level.

FIG. 9 is a schematic data flow diagram illustrating connections betweenelectrodes (e.g., electrodes 102, 108), an impedance analyzer 123 (e.g.,the Keysight E4990) with four terminal connections, and a computingdevice 125 configured to determine physical characteristics of the MUTsample 101. In this embodiment, there are two terminal connections onthe impedance analyzer 123, which transmits a current signal (overconductor 132) over a range of frequencies to the transmitting electrode(e.g., transmitting electrode 102). This signal passes through the MUT101 to the receiving electrode (e.g., receiving electrode 108) and istransmitted back to the analyzer 123 via a conductor 131. The voltage ofthe transmitting electrode (e.g., transmitting electrode 102) ismeasured by the analyzer 123 using conductor 134. The voltage of thereceiving electrode (e.g., receiving electrode 108) is measured by theanalyzer using the conductor 133. The analyzer 123 generates a value ofan impedance characteristic over the range of frequencies of thetransmitted signal. This impedance value for each specific frequency istransmitted (as data shown by 124) to the computing device 125. Thecomputing device 125 is configured to determine characteristics of theMUT sample 101 based upon these impedance values. The computing device125 can include any conventional computing architecture capable ofperforming processes as described herein and can be programmed toperform particular functions. The computing device 125 can include oneor more processors and a memory, which may store program code and/orprogram logic for performing various functions according to embodiments.The system ground 135 of the impedance/analyzer 123 is connected to thetransmitting conductive backer ground plate (e.g., transmittingconductive backer ground plate 103) and the receiving conductive backerground plate (e.g., receiving conductive backer ground plate 109). Theelectrical connections illustrated in FIG. 9 can be similarly applied tosystems 200, 300, 300A, 400, 500 and 900.

The correlation between an impedance characteristic and a physicalcharacteristic may be developed with any number of well-knowncorrelation methods such as analysis of variations (ANOVA), neuralnetworks, multiple regressions, and deep learning. A determination as towhich correlation process, which impedance characteristic(s), and whichfrequency range may result in the best correlation would be decidedbased upon the mix of variables that provides the most statisticallysignificant results.

The test data can be gathered using standard ASTM tests such as D4818,D422, D698, and D1557. Additional physical properties that may beincluded in the data for the algorithm development are the mass of wateradded to the dried soil, the mass of the dried soil, and the compactionvolume (compressed sample height).

FIG. 10 is a schematic cross-sectional depiction of system 400,illustrating electric field lines 116 relative to the respective backerground plates 403, 409. A first subset 116A of the electric field lines116 are shown as traveling perpendicularly (relative totransmitting/receiving surfaces) directly from the transmittingelectrode 402 to the receiving electrode 408. As the transmittingelectrode 402 has a larger area (e.g., diameter in the case of acircular electrode, or surface area in the case of another shape) thanthe receiving electrode 408, and the receiving backer ground plate 409is in the same plane as the receiving electrode 408 (and surrounds thereceiving electrode), an additional subset 116B of the electric fieldlines 116 are shown travelling perpendicularly from the transmittingelectrode 402 to the receiving electrode backer ground plate 409. Inthis configuration, the receiving electrode backer ground plate 409 actsas a guard to the field lines 116A traversing between the transmittingelectrode 402 and the receiving electrode 408 and ensures that the fieldlines 116A going directly from the transmitting electrode 402 to thereceiving electrode 408 are perpendicular to the electrode surfaces. Anadditional subset 116C of field lines 116 from the transmittingelectrode 402 are transmitted to the transmitting conductive backerground plate 403 and pass through the MUT sample 101. These field lines116C affect the parasitic capacitance load on the transmitting electrode402, but do not affect the field lines 116A that produce the measurementdata.

An additional view of system 500 is shown in an enlarged cross-sectionaldepiction in FIG. 11, which additionally illustrates electromagneticfield lines. As in the depiction of system 500 in FIG. 6, thetransmitting electrode 502 has a transmitting area (e.g., diameter inthe case of a circular electrode) that is greater than the ID of thecontainer (including the outer segments 531 and 532 and the linersegments 533 and 534). In these implementations, the lower liner 533 (orupper liner 534) can include a seat for supporting an overhang portionof the transmitting electrode 502 extending beyond the ID of thenon-liner of the container. The interactions of the field lines 116 aresimilar to those described with reference to system 400 in FIG. 10. Insystem 500, the supporting member 119 (FIGS. 1, 3, 5, and 7) may not berequired to support the transmitting electrode 502 and adjoining backerground plate 503. This embodiment is a simple mechanical change and doesnot affect any of the electrical performance previously described.

The impedance of materials, for example, soils, is a complex quantitymade up of contributions of the resistance and capacitance of the soilwhen an oscillating electromagnetic signal is passed through it. Theequation for this isZ=Z _(R) +Z _(C)where Z is the total impedance, Z_(R) is the impedance component due tothe resistance, and Z_(C) is the impedance component due to thecapacitance. For the range of frequencies used for soil testing, theinductive effects of the soil are negligible. Z_(R) and Z_(C) are givenby the following relations:

${Z_{R} = R}{Z_{C} = \frac{1}{i\omega C}}$where R is the resistance and C is the capacitance. The capacitance C isgiven the following relation:C=ε _(r)ε₀[A _(R) /H _(sample)]where ε_(r) is the relative permittivity of the soil (also called thedielectric), ε₀ is a constant permittivity of free space, A_(R) is thearea of the receiving electrode (e.g. receiving electrodes 108, 308,408, or 508), and H_(sample) is the height of the sample and also thedistance between the electrodes. The values of Z, Z_(R), and Z_(C) areall functions of the properties of the soil, the compaction level(density) of the soil, the moisture level of the soil, and the frequencyof the electromagnetic signal.

FIG. 12 illustrates examples of field lines 116A and 116B modeled usingComsol Multiphysics for system 300A in FIG. 4. In this example, the MUTsample 101 (e.g., soil) has a height of 20 mm (about three quarters ofan inch) and an ε_(r) (dielectric) value of 10. A dielectric value of 10is typical of a soil with a low moisture level. Soil solids have adielectric value of about 7. Water has a dielectric value of about 80.In this embodiment, upper section 332 and lower section 331 of thecylinder are constructed out of poly methyl methacrylate (PMMA oracrylic) to allow for visual observation of the testing process. Uppersection 332 and/or lower section 331 can also be formed of othernon-conducting materials such as conventional plastics or glass, such asplastics like polyester, polyethylene, polyvinyl chloride (PVC),polytetrafluoroethylene (Teflon), poly carbonate, and composites likevarious fiber glass reinforce epoxy laminate materials (e.g. FR-4). Ascan be seen, the electric field lines 116A between the transmittingelectrode 302 and receiving electrode 308 are perpendicular to theelectrodes with no non-linear deviations. These field lines 116A producethe impedance characteristic data for the MUT sample 101. The electricfield lines 116B between the transmitting electrode 302 and thereceiving backer ground plate 309 and are also perpendicular to theground plates 303, 309 and the transmitting electrode 302 with nonon-linear deviations.

FIG. 13 illustrates a system 900 according to various additionalembodiments. In these embodiments, system 900 is configured for use indetermining impedance characteristics of a solid MUT 901 without the MUT901 being placed in an electrically non-conducting container (e.g.,container 104, FIG. 3). In some cases, the solid MUT 901 includes aconcrete or asphalt sample, such as a cured concrete cylinder or asphaltcore.

Referring to FIG. 13, the solid MUT 901 is placed directly on atransmitting electrode assembly 911, which is supported by electricallynon-conducting support(s) 904, which are in turn supported on anunderlying structure 906 such as a floor, tabletop, or platform. Areceiving electrode assembly 910 is placed on top of the solid MUT 901.Additional electrically non-conducting support(s) 905 can be placed ontop of the solid MUT 901 and provide mechanical support for thereceiving electrode assembly 910 (e.g., such that the non-conductingsupports 904 and 905 include slots or ledges for supporting thecorresponding electrode assemblies 910, 911). In various embodiments,the electrode assemblies 910 and 911 are positioned such that the centerof each of the transmitting electrode 902 and the receiving electrode908 are aligned. In some particular embodiments, the non-conductingsupports 904 and 905 are separate components, however, in some cases,one or more non-conducting lower supports 904 can be coupled with (orsubstantially unitary with) one or more non-conducting upper supports905. In various particular embodiments, the solid MUT 901 has a greaterwidth (or diameter, depending upon its shape) than the outer dimensionof the backer ground plates 903, 909, such that a portion of the solidMUT 901 extends outside of the outer dimension of the electrodeassemblies 910, 911. In some cases, lower support 904 can include a slotor shelf for supporting the transmitting electrode assembly 911.Additionally, or alternatively, in some embodiments, the upper support905 can also include a slot or shelf for supporting the receivingelectrode assembly 910. In some cases, as shown in FIG. 13, the supports904 and 905 may extend radially beyond the MUT 901 and be aligned by useof guide rods 940.

As noted herein, the capacitive volumes 920 and 930 enclosed by theelectrode assemblies 910 and 911 are controllable to optimize theparasitic capacitances resulting from the effects of the electromagneticfield lines which emanate from both the transmitting electrode 902 andthe receiving electrode 908, and go to the backer ground plates 903 and909, and the field lines that pass through the MUT 901 and go to thereceiving backer ground plate 909.

FIG. 14 illustrates electrical circuit connections in system 900 (FIG.13). As shown, these electrical circuit connections may resemble thosein the circuit diagram of system 200 depicted in FIG. 8. As shown inFIG. 14, however, the solid MUT 901 may extend outside of the outerdimension of the electrode assemblies 910 and 911.

It is understood that while various embodiments illustrate and describetransmitting electrodes (e.g. 102, 302, 402, 502 and 902) and respectivereceiving electrodes (e.g. 108, 308, 408, 508 and 908) as oriented inparticular manners, it is understood that these orientations could bemodified without modifying the teachings of the disclosure. For example,electrodes orientations can be reversed (e.g., transmitting electrodesplaced above receiving electrodes), or entire orientations of systemsdisclosed herein can be altered (e.g., such that transmitting/receivingelectrodes are aligned on the same horizontal plane, or at any anglerelative to normal).

In various particular embodiments, electrodes shown and described have acircular (or nearly circular, within margins of measurement error)transmitting/receiving surface. That is, discussions of variation in thetransmitting/receiving area of these electrodes necessarily relates to avariation in the diameter of these surfaces. However, as describedherein, in other embodiments, the transmitting and/or receivingelectrode surfaces may take other forms (e.g., elliptical, rectangular,rectangular with rounded corners).

The design of the individual electrodes in the various arrays discussedwith reference to one or more FIGURES may be circular in shape. However,in some embodiments, a circular-shaped electrode may limit the potentialof field concentration available if the desired area of detection in theMUT included a corner or a point. In various embodiments, at least oneof the electrodes has an ellipsoid shape. In various other embodiments,as noted herein, at least one of the electrodes has a rectangular shapewith rounded corners. In various embodiments, the electrodes may have auniform area to match their signal generation capacity withcorresponding receiving capacity. In some cases, the diameter of theelectrodes relative to the distance between the centers of theelectrodes may vary. The Applicants have further discovered that theremay be a tradeoff between the electric field strength of the array, thegeometry factor of the array, and the signal-to-noise ratio of themeasurement obtained by the array. Applicants have further discoveredthat these factors are not determinant a priori to establish the optimumarea of the electrode.

Various approaches described allow for determining a physical propertyof one or more portions (e.g., sub-voxel or a number of sub-voxels) ofthe MUT 101, e.g., as described in U.S. Pat. Nos. 9,465,061 and9,804,112 (each of which is herein incorporated by reference in itsentirety). In various embodiments, a number of measurements of thephysical property(ies) of interest are measured by conventional meansand correlated with the measured variations of the measured (andcomputed) complex impedance (of the MUT, including one or more voxelsand sub-voxels) using the apparatuses/systems/approaches describedherein. In various embodiments, the number of measurements can besufficiently large such that the resulting correlation is statisticallysignificant. The impedance measurements can be made with the same typeof array that will be used to inspect unknown MUTs, or in otherembodiments, a parallel plate electrode arrangement may be used.Regardless of the array geometry, the measurements may also be made overa range of frequencies. Further embodiments include a method ofdeveloping an algorithm to correlate the physical property to themeasured impedance (of the voxel or sub-voxel over the selected range offrequencies), which may use any number of well-known correlation methodssuch as analysis of variations (ANOVA), neural networks, multipleregressions, and deep learning. A determination as to which process,impedance characteristic(s) and frequency range may ensure that the bestfit may be made by selection of the one that provides the moststatistically significant results.

In various embodiments, components described as being “coupled” to oneanother can be joined along one or more interfaces. In some embodiments,these interfaces can include junctions between distinct components, andin other cases, these interfaces can include a solidly and/or integrallyformed interconnection. That is, in some cases, components that are“coupled” to one another can be simultaneously formed to define a singlecontinuous member. However, in other embodiments, these coupledcomponents can be formed as separate members and be subsequently joinedthrough known processes (e.g., fastening, ultrasonic welding, bonding).

The terminology used herein is for the purpose of describing particularexample embodiments only and is not intended to be limiting. As usedherein, the singular forms “a”, “an” and “the” may be intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. The terms “comprises,” “comprising,” “including,” and“having,” are inclusive and therefore specify the presence of statedfeatures, integers, steps, operations, elements, and/or components, butdo not preclude the presence or addition of one or more other features,integers, steps, operations, elements, components, and/or groupsthereof. The method steps, processes, and operations described hereinare not to be construed as necessarily requiring their performance inthe particular order discussed or illustrated, unless specificallyidentified as an order of performance. It is also to be understood thatadditional or alternative steps may be employed.

When an element or layer is referred to as being “on”, “engaged to”,“connected to” or “coupled to” another element or layer, it may bedirectly on, engaged, connected or coupled to the other element orlayer, or intervening elements or layers may be present. In contrast,when an element is referred to as being “directly on,” “directly engagedto”, “directly connected to” or “directly coupled to” another element orlayer, there may be no intervening elements or layers present. Otherwords used to describe the relationship between elements should beinterpreted in a like fashion (e.g., “between” versus “directlybetween,” “adjacent” versus “directly adjacent,” etc.). As used herein,the term “and/or” includes any and all combinations of one or more ofthe associated listed items.

Spatially relative terms, such as “inner,” “outer,” “beneath”, “below”,“lower”, “above”, “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. Spatiallyrelative terms may be intended to encompass different orientations ofthe device in use or operation in addition to the orientation depictedin the figures. For example, if the device in the figures is turnedover, elements described as “below” or “beneath” other elements orfeatures would then be oriented “above” the other elements or features.Thus, the example term “below” can encompass both an orientation ofabove and below. The device may be otherwise oriented (rotated 90degrees or at other orientations) and the spatially relative descriptorsused herein interpreted accordingly.

The functionality described herein, or portions thereof, and its variousmodifications (hereinafter “the functions”) can be implemented, at leastin part, via a computer program product, e.g., a computer programtangibly embodied in an information carrier, such as one or morenon-transitory machine-readable media, for execution by, or to controlthe operation of, one or more data processing apparatus, e.g., aprogrammable processor, a computer, multiple computers, and/orprogrammable logic components.

A computer program can be written in any form of programming language,including compiled or interpreted languages, and it can be deployed inany form, including as a stand-alone program or as a module, component,subroutine, or other unit suitable for use in a computing environment. Acomputer program can be deployed to be executed on one computer or onmultiple computers at one site or distributed across multiple sites andinterconnected by a network.

Actions associated with implementing all or part of the functions can beperformed by one or more programmable processors executing one or morecomputer programs to perform the functions of the calibration process.All or part of the functions can be implemented as, special purposelogic circuitry, e.g., an FPGA and/or an ASIC (application-specificintegrated circuit). Processors suitable for the execution of a computerprogram include, by way of example, both general and special purposemicroprocessors, and any one or more processors of any kind of digitalcomputer. Generally, a processor will receive instructions and data froma read-only memory or a random-access memory or both. Components of acomputer include a processor for executing instructions and one or morememory devices for storing instructions and data.

This written description uses examples to disclose the invention,including the best mode, and also to enable any person skilled in theart to practice the invention, including making and using any devices orsystems and performing any incorporated methods. The patentable scope ofthe invention is defined by the claims, and may include other examplesthat occur to those skilled in the art. Such other examples are intendedto be within the scope of the claims if they have structural elementsthat do not differ from the literal language of the claims, or if theyinclude equivalent structural elements with insubstantial differencesfrom the literal languages of the claims.

We claim:
 1. A system for measuring an electromagnetic impedancecharacteristic of a material under test (MUT), the system comprising: anelectrically non-conducting container sized to hold the MUT, theelectrically non-conducting container having a first opening at a firstend thereof and a second opening at a second, opposite end thereof; atransmitting electrode assembly at the first end of the electricallynon-conducting container, the transmitting electrode assembly having: atransmitting electrode with a transmitting surface; and a transmittingelectrode backer ground plate at least partially surrounding thetransmitting electrode, the transmitting electrode backer ground platebeing electrically grounded and insulated from the transmittingelectrode, wherein the transmitting electrode backer ground plateextends from a plane formed by the transmitting electrode and creates anelectrically isolated volume proximate to the transmitting electrode;and a receiving electrode assembly at the second end of the electricallynon-conducting container, the receiving electrode assembly having areceiving electrode with a receiving surface, wherein the receivingelectrode is approximately parallel with the transmitting electrode, andwherein the transmitting surface of the transmitting electrode is largerthan the receiving surface of the receiving electrode.
 2. The system ofclaim 1, wherein the transmitting electrode backer ground plate isformed of an electrically conductive material and comprises a recesscorresponding with the transmitting electrode, and wherein the planeformed by the transmitting electrode is substantially parallel with asurface of the MUT.
 3. The system of claim 1, wherein the receivingelectrode assembly further comprises: a receiving electrode backerground plate at least partially surrounding the receiving electrode, thereceiving electrode backer ground plate being electrically grounded andinsulated from the receiving electrode, wherein the receiving electrodebacker ground plate extends from a plane formed by the receivingelectrode and creates an electrically isolated volume proximate to thereceiving electrode, wherein the receiving electrode backer ground plateis formed of an electrically conductive material and comprises a recesscorresponding with the receiving electrode, and wherein the plane formedby the receiving electrode is substantially parallel with a surface ofthe MUT, wherein the receiving electrode backer ground plate extendsalong a front face of the receiving electrode assembly, wherein thefront face is coplanar with the plane formed by the receiving electrode.4. The system of claim 1, wherein during operation of the system, thetransmitting electrode and the receiving electrode are in directphysical contact with the MUT and either electrically non-conductivewith the MUT or electrically conductive with the MUT.
 5. The system ofclaim 1, further comprising: a signal generator/analyzer coupled withthe transmitting electrode and the receiving electrode, the signalgenerator/analyzer comprising a generator component configured toinitiate transmission of a set of electromagnetic signals over a rangeof frequencies from the transmitting electrode, through the MUT, to thereceiving electrode, and an analyzer component configured to detect achange in the set of electromagnetic signals from the transmittingelectrode to the receiving electrode; and a computing device coupledwith the signal generator/analyzer, wherein the computing device isconfigured to determine a characteristic of the MUT based upon thechange in the set of electromagnetic signals from the transmittingelectrode to the receiving electrode, wherein determining thecharacteristic of the MUT comprises: determining a difference in anaspect of the set of electromagnetic signals; comparing the differencein the aspect to a predetermined threshold; and determining thecharacteristic of the MUT based upon the compared difference.
 6. Thesystem of claim 1, wherein the transmitting electrode and the receivingare aligned parallel to one another.
 7. The system of claim 1, whereinthe electrically non-conducting container has a cylindricalcross-section, rectangular cross-section, or oblong cross-section, takenin a direction perpendicular to a primary axis thereof, and wherein theelectrically non-conducting container comprises an inner liner formed ofan electrically non-conducting material.
 8. The system of claim 1,wherein the electrically non-conducting container includes at least twodistinct sections, wherein the transmitting electrode has a diameterlarger than an inner diameter of the electrically non-conductingcontainer, and wherein one of the at least two distinct sectionscomprises a seat for supporting an overhang portion of the transmittingelectrode.
 9. The system of claim 1, wherein the transmitting electrodeassembly and the receiving electrode assembly are shaped to coincidewith a cross-sectional shape of the first opening and second opening,respectively, of the electrically non-conducting container.
 10. Thesystem of claim 1, wherein the transmitting electrode assembly and thereceiving electrode assembly are substantially contained within theelectrically non-conducting container.
 11. The system of claim 1,wherein the transmitting electrode assembly and the receiving electrodeassembly are sized to complement an opening in a soil compaction device.12. The system of claim 1, wherein the MUT comprises a soil, a granularmaterial or wet concrete.
 13. The system of claim 1, wherein the MUTcomprises a liquid including organic or inorganic compounds.
 14. Thesystem of claim 1, wherein the set of electromagnetic signals aretransmitted over a frequency range of approximately 100 kHz to 100 MHz.15. A method for determining an electromagnetic impedance characteristicof a material under test (MUT), the method comprising: placing the MUTin a testing system comprising: an electrically non-conducting containersized to hold the MUT, the electrically non-conducting container havinga first opening at a first end thereof and a second opening at a second,opposite end thereof; and a transmitting electrode assembly at the firstend of the electrically non-conducting container, the transmittingelectrode assembly having a transmitting electrode with a transmittingsurface, sealing a bottom of the electrically non-conducting container;placing a receiving electrode assembly at the second end of theelectrically non-conducting container over the MUT, the receivingelectrode assembly having a receiving electrode with a receivingsurface, wherein the receiving electrode is approximately parallel withthe transmitting electrode, and wherein the transmitting surface of thetransmitting electrode is larger than the receiving surface of thereceiving electrode; transmitting a set of electromagnetic signals overa range of frequencies from the transmitting electrode, through the MUTto the receiving electrode; and determining a characteristic of the MUTbased upon a change in the set of electromagnetic signals from thetransmitting electrode to the receiving electrode.
 16. The method ofclaim 15, wherein the set of electromagnetic signals are transmittedover a frequency range of approximately 100 kHz to 100 MHz.
 17. Themethod of claim 15, further comprising compacting the MUT prior toplacing the receiving electrode assembly at the second end of theelectrically non-conducting container over the MUT, wherein thecompacting comprises placing a compression weight in direct physicalcontact with the MUT.
 18. A system for measuring an electromagneticimpedance characteristic of a material under test (MUT), the systemcomprising: at least one electrically non-conducting support sized tophysically support the MUT; a transmitting electrode assembly positionedon a first side of the MUT, the transmitting electrode assembly having:a transmitting electrode with a transmitting surface; and a transmittingelectrode backer ground plate at least partially surrounding thetransmitting electrode, the transmitting electrode backer ground platebeing electrically grounded and insulated from the transmittingelectrode, wherein the transmitting electrode backer ground plateextends from a plane formed by the transmitting electrode and creates anelectrically isolated volume proximate to the transmitting electrode;and a receiving electrode assembly positioned on a second side of theMUT opposite the first side of the MUT, the receiving electrode assemblyhaving a receiving electrode with a receiving surface, wherein thereceiving electrode is approximately parallel with the transmittingelectrode, and wherein the transmitting surface of the transmittingelectrode is larger than the receiving surface of the receivingelectrode.
 19. The system of claim 18, wherein the MUT is a solidmaterial, and wherein an outer dimension of the MUT extends beyond anouter dimension of the at least one electrically non-conducting supportsuch that the at least one electrically non-conducting support does notenvelop the MUT.
 20. The system of claim 18, wherein the transmittingelectrode and the receiving are aligned parallel to one another.